Outer membrane protein A of Escherichia coli forms temperature-sensitive channels in planar lipid bilayers

AbstractThe temperature dependence of single-channel conductance and open probability for outer membrane protein A (OmpA) of Escherichia coli were examined in planar lipid bilayers. OmpA formed two interconvertible conductance states, small channels, 36–140 pS, between 15 and 37°C, and large channels, 115–373 pS, between 21 and 39°C. Increasing temperatures had strong effects on open probabilities and on the ratio of large to small channels, particularly between 22 and 34°C, which effected sharp increases in average conductance. The data infer that OmpA is a flexible temperature-sensitive protein that exists as a small pore structure at lower temperatures, but refolds into a large pore at higher temperatures